Multiple computer systems and peripheral input/output systems are often interconnected to allow data to be transferred among the various systems. Several different types of interconnect means are commonly used to connect to the multiple computer and peripheral systems, hereinafter referred to as "nodes." An interconnect may comprise a single data channel, referred to as a serial data interconnect, or the interconnect may comprise multiple data channels, referred to as a parallel data interconnect. Each node may typically drive signals onto the interconnect that are then received by one or more of the other interconnected nodes. The various nodes may be physically close together, or they may be widely separated.
The interconnect means comprises a conductor means that interconnects each of the nodes. The conductor means may be copper wires, such as twisted pairs or coaxial wires, fiber optic cables, or infrared emissions, for example. Signal transmission through the conductor means may be distorted due to deterioration over long distance, or interfering voltage or radiation fields that couple onto the conductor means, for example. A well known method of overcoming transmission distortion is the use of complimentary signals, in which the driving node drives both a signal and a compliment of the signal, where the compliment signal is typically an inversion of the signal. Transmission distortion then generally effects both signals in a common manner, which is referred to as "common mode distortion." The receiving nodes then compare the signal and the compliment signal so that the effects of common mode transmission distortion may be overcome.
Nodes that are interconnected with wire may be subject to differences in ground potential, referred to as "ground shift", between the nodes. When this occurs, a voltage signal impressed on the wire by the active driver circuit in a driving node may appear as a much larger voltage at the quiescent driver(s) of the receiving node(s).
Transmission distortion or ground shifts may cause the voltage on the terminals of a driver circuit to exceed the breakdown rating of the output transistors.
Accordingly, it is an object of the present invention to prevent voltage breakdowns in the driver circuit of an integrated circuit which has complimentary signal output terminals.
Another object of the invention is to provide a means for preventing voltage breakdowns in the driver circuit of an integrated circuit which has complimentary output terminals that requires less space on the integrated circuit than prior art solutions.
Other objects and advantages will be apparent to those of ordinary skill in the art having reference to the following figures and specification.